We are engaged in an attempt to predict response to stimulant medication in hyperkinetic children. This is a proposal for supplemental medication support so that pilot studies can be done prior to an investigation of methylphenidate dose/response curves. Pilot studies will be used to develop an event related potential paradigm that will provide psychophysiological measures of various aspects of selective attention under varying task load. Other pilot studies will be done to develop clinical rating procedures that can be applied to investigation of stimulant response in adults and adolescents.